1. Technical Field
The present invention relates to backrest inclination structures for lumbar support and, more particularly, to a backrest inclination structure providing lumbar support and operating in conjunction with a backrest adjustment mechanism positioned at a chair laterally. When in use, the backrest inclination structure can be operated easily to adjust a backrest of the chair and can attain the most comfortable position of the backrest by pressing the human back against the backrest under the weight of the human back. Furthermore, the backrest inclination structure not only enables the human back to conic into tight contact with the adjusted backrest, but also enables the backrest adjustment mechanism to be fixed in place again, thereby simplifying the backrest adjustment assembly and enhancing the comfort provided by the backrest.
2. Description of Related Art
To enable existing chairs to provide maximum comfort to sitters, related manufacturers usually consider equipping a chair with a motion adjustment mechanism whereby a cushion unit, a backrest unit, and an armrest unit of the chair can undergo directional adjustment as needed, to enhance the flexibility of use of the chair.
An angle-adjusting structure for a backrest of a chair disclosed in U.S. Pat. No. 7,802,847 is implemented in the form of an angle-adjusting structure mounted at a rear side of a butterfly-shaped mounting member of the chair. The angle-adjusting structure includes a shaft having external teeth and passing through internal holes of a main body and a rotating member. A resilient element mounted around an end of the shaft, A cover is secured to the main body by a threaded fastener. A pressing member is mounted on an opposite end of the shaft adjacent to an outer wall of the main body. Thus, by pressing the pressing member inward, the external teeth of the shaft are disengaged from the internal teeth of the rotating member, allowing the rotating member to enter a free state for adjusting to any angle. When the pressing member is released, the resilient element mounted around the end of the shaft extends outward to re-engage the external teeth of the shaft with the internal teeth of the rotating member, thereby securing the rotating member in place.
Although the aforesaid angle-adjusting structure for the backrest of the chair allows the backrest of a chair to undergo anticipated angle adjustment when in use, only a portion of the backrest can be in contact with the human back while the adjustment of the inclination of the backrest is taking place, not to mention that the angle-adjusting structure for the backrest of the chair comprises many constituent components which complicate an assembly process and thus incur high costs in the manufacturing process of the chair.